The proposed research project investigates new family forms and their implications for adults, children and the population-level reproduction of family change. It rests fundamentally on three premises: 1) standard definitions and categories are no longer adequate to represent the reality of family life; 2) static comparisons overlook transitions both within and across family types key to understanding new family forms; 3) ignoring the context in which individuals form and transform families misses a crucial piece of what is needed to make sense of family change. This project pays close attention to heterogeneity within categories commonly applied in family research, looking, for example, at distinctions between never-married and divorced mothers, cohabiting and married two-parent families, and high and low conflict two-parent families. It addresses the dynamic nature of families, tracing change over time both within and across family types. In addition, it situates individuals within families, neighborhoods, and other social contexts that affect their attitudes and behaviors. It relies on new data from three complementary sources: the National Survey of Family Growth (NSFG), the National Survey of Families and Household (NSFH), and the Los Angeles Family and Neighborhood Survey (L.A.FANS). The development plan outlined in this application is specifically designed to accomplish the following five objectives: 1) acquire skills in interactions-based models; 2) gain expertise in survey research methods; 3) expand the scope of current research to include perspectives from public health, economics, and law; 4) present new work at scholarly conferences and publish in leading journals; and 5) prepare a grant application to support an independent research program. Training components include mentorship, participation in the California Center for Population Research (CCPR) at the University of California-Los Angeles (UCLA), an apprenticeship in survey methods with the L.A.FANS, and additional coursework. This research and training application builds on past work, expanding its scope and bringing new tools to bear on questions at the intersection of family, policy, and social inequality.